Rectifiers are operative to rectify alternating-current (AC) power to direct-current (DC) power. Such a rectifier is preferably used together with an AC generator to be installable in motor vehicles.
Specifically, a rectifier used together with an AC generator works to rectify AC power generated by the AC generator to DC power to be used for electric loads.
A rectifier used together with an AC generator installable in motor vehicles is normally provided with at least one rectifying element and a fin-shaped heatsink, such as a cooling fin. The at least one rectifying element is fitted in the cooling fin by pressing it thereinto.
In order to prevent breakage during the press fitting, a rectifier with a portion around a hole in which at least one rectifying element is to be fitted being greater in thickness than another portion is disclosed in US Patent Application Publication No. 2007/0046114A1 corresponding to Japanese Patent Application Publication No. 2007-068257.
On the other hand, automotive AC generators have higher output power with increase in power requirement of electric loads. With increase in power requirement of electric loads, an output line drawn out from an output terminal of an AC generator has a greater cross section so as to suppress the increase in current density through the output line. This results in increasing the weight of the output line.
Rectifiers normally include a plurality of pairs of positive and negative (high-side and low-side) rectifying elements and positive and negative cooling fins in which the positive and negative rectifying elements are mounted, respectively. Normal rectifiers also include a terminal block assembly made up of a plurality of terminal blocks. Leads drawn out from one pair of the positive and negative rectifying elements are joined to a conductive member (preformed metal insert), and the conductive member is connected to one end of a corresponding one phase winding of a stator of the AC generator. The conductive members (preformed metal inserts) for respective pairs of the positive and negative rectifying elements are resin molded to be integrated with each other to form the terminal block.
Each normal rectifier constitutes a bridge circuit for full-wave rectifying a multiphase alternating current, such as three-phase alternating current.
As an output terminal of a rectifier drawn out from the positive cooling fin, which serves as the output terminal of the AC generator, a bolt is normally used so that the terminal of the output line is threadedly fastened to the output terminal of the AC generator with a nut.
The increase in the output power of an AC generator requires the increase in the diameter of the bolt and the increase in the size of the bolt thread to thereby increase the clamping force due to the set of the bolt and nut. This secures the reliability of the electrical connection between the rectifier (AC generator) and the output line.
In such a normal rectifier installed in a motor vehicle together with an AC generator, engine vibrations may be transferred to the output line drawn out from the output terminal of the AC generator. In this situation, vibration load of the output line increases with increase in the diameter and weight of the output line. The vibration load of the output line is carried to the output terminal of the AC generator to which the output line is directly fastened so that the vibration load acts on a portion of the positive cooling fin located adjacent to the output terminal of the AC generator.
The vibration load acting on the portion of the positive cooling fin located adjacent to the output terminal of the AC generator applies vibration load to a positive rectifying element located close to the portion of the positive cooling fin.
A difference between the vibration phase of a conductive member connected to the positive rectifying element located close to the portion of the positive cooling fin located adjacent to the output terminal of the AC generator and that of the positive cooling fin may cause vibration load to periodically act on the positive rectifying element via its lead connected to the conductive member. This may damage the positive rectifying element, and/or reduce the life thereof.
In order to suppress the increase in current density through the output line without increasing in the diameter thereof, the AC generator has a higher output voltage. This approach however may cause new problems, such as increase in leakage current inside either the AC generator or each electric load, occurrence of arc discharge, and the like.
The increase in the size of the bolt thread so as to provide sufficient rigidity to the connection between the terminal of the output line and the output terminal of the AC generator may apply load on the positive cooling fin located adjacent to the output terminal of the AC generator. Cooling fins are normally manufactured from a pressing-processable or diecasting-moldable flexible material, such as aluminum or copper so that they are deformable. For this reason, the load applied to the positive cooling fin may result in deformation of the positive cooling fin.
This may damage the positive rectifying elements fitted in the positive cooling fin, and/or reduce the life of each of the positive rectifying elements.